This paper discusses the development of a knowledge-based system (KBS) for the exploration and production (E&P) business based on a domain specific ontology. The E&P is one that is fraught with high employee turnover due to volatile market trends. The introduction of a KBS to capture the knowledge of industry experts will aid the preservation of knowledge assets within the organisation. In order to ensure the comprehensiveness of the captured knowledge and that the knowledge is interpreted within the correct context, an ontology was developed prior to the development of the KBS. The KBS, called the Expert Directory System (EDS), was then developed based on the ontology and this paper includes a discussion on the EDS implementation.